Switchboard and supervisory signal circuit.



- Patented Nbv. 4. I902. D. S. HULFISH.

SWITQHBO ARD AND SUPERVISORY SIGNAL CIRCUIT.

(Application filed July 1, 1902.)

(No Model.)

ATTORNEY.

THE Mom's wzrzns 00., Ppomgnum wnsumamu. n. q.

NITED STATES ATEN'I OFFICE.

DAVID S. HULFISH, OF CHICAGO, ILLINOIS, ASSIGNO'E TO AMERICAN TELE-PHONE AND TELEGRAPH COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OFNEW YORK.

SVVITCHBOARD AND SUPERVISORY SIGNAL CIRCUIT;

SEEGLFIGATXON forming part of Letters Patent N 0. 712,801, datedNovember 4, 1903i.

Application filed July 1, 1902. Serial No 113,972. (No model.)

[ a whom/ it may concern: plugs, and the said local circuits are com- Beit known that 1, DAVID S. HULFIsH, re- 'pleted through suitableresistance when the siding at Chicago, in the county of Cook and plugsareinserted in main-circuitswitch-sock- State ofIllinois, have inventedcertain Imets. Signal devicesgenerally small glowprovements inSwitchboard and Supervisory lamps, one associated with each switch-plug55 Signal Circuits, of which the following is a are included in theselocal circuits, and the specification. said lamps are provided withcontrolling- Thisinvention relates to the central-station shuntsextending around them and leading apparatus of telephone-exchanges, andespethrough the local switching or contact points cially to'theconstruction and arrangement of of corresponding relays, also one foreach 69 the lamp or other signals which are associated plug, whichrelays are connected in the mainwith switch-cords and which enable theopcircuit switch-cord loops. The relays are erators to exerciseintelligent supervision thus responsive to the operation of the hookovercalls and over connections between two switches pursuant to the removaland replacesubstations at any or all stages of the Operament of thereceivers at the respective substa- 6; tion. tions, and by closing andopening the shunt- In standard central-station telephone syscircuits inresponse to such operation permit tems and apparatus as at presentgenerally the displayof the lamp-signal associated with constituted andemployed the main or subany plug when the receiver is on its hook atstation circuits when inactive are conduc-. the substation of aline inwhose socket such 70 tively open or discontinuous, but when theplugisinserted, but causes the Same to remain substation-receiver istaken from the switchundisplayed or be withdrawn when the said book areclosed by the action of said switch, receiver is removed from the hook.These which therefore controls the continuityot the lamp-signals aretermed supervisory sigcircuit. nals and the relays controlling them su-75 The Switch-cords whereby any two main p'ervisory relays. Thedisplayof the signal circuits may be united at the central stationassociated with either plug indicates, thereare provided with terminalswitch-plugs, one fore, that the receiver at the substation of the ofwhich, usually termed the answeringline directly connected with suchplug is on plug, isinsertedin aswitch-socket of the callits hook, andthe absence of such signal dis- 8o originating substation-circuit,whilethe other, .play indicates that the receiver has been rewhich may betermed the companion plug, moved from the hook. Such indication has, isSimilarly placed in a switch-socket ot' the however, been foundinsufficient, since in the called or wanted main circuit. Eachswitchcase of a called subscriber the signal is the 5 cord has twomain-circuit conductors, which same whether the said subscriber hasfailed 85 when the plugs are thus inserted extend reto respond at all bytaking up his receiver or spectively between the main conductors ofwhether he has answered by such action and the two substation-circuitsconcerned; but has thenforsomereason replaced hisreceiver, as theworking battery or other source of curyet in the former instance theoperator'is re- 0 rent-supply is bridged between the said mainquired toring up the wanted substation again 0 cord conductors it follows thatthe main-cirand in the latter case is not so required. To cuitconductorsof the switch-cord are formed remedy this insufficiency and theconfusion thereby into two main-circuit loops, each liable to be causedthereby and to provide closed at its inner extremity through the saidfully discriminative signals are the objects of 5 source and eachextending to its respective this invention. 5 plug and adapted therebyto constitute a ter- To this end the invention consists, mainly, minalloop, through which the main circuitin in providing an additionallocal-circuit conwhose switch-socket the plug is inserted is or ductorfor the companion plug, in controlling may be closed. The Switch-cordsystem also this by the relay of said plug, and-in an elechas alocal-circuit conductor for each of its tromagnetic switch connectedtherein and too adapted when actuated by the operation of said relay toconnect both signals in parallel branches of the local circuit of theansweringplug, to extend the controlling-shunt of the supervisory signalof the said answering-plug and establish said shunt around both-signals,and to lead said shunt thusextendedthrough the local or contact pointsof both supervisory relays, so that the de'e'nergization of either relaypursuant to the replacement of the receiver on its hook at thesubstation of the circuit containing such relay and the consequentopening of the extended shunt-circuit will cause the simultaneousdisplay of both supervisory signals and will thus furnish anunmistakable signal for disconnection which cannot by any possibilitymean anything else.

It consists also in certain details of construction and arrangement ofthe said circuit connections and apparatus, and provides also that thesaid electromagnetic switch shall after it has been energized be enabledto transfer its own local circuit from the contacts of the companionplug relay to a new path through contacts controlled by its own magnet,thereby leaving said relay free to participate in the direct control ofthe supervisory signals.

The drawing which accompanies and illustrates this specification is adiagram representing a modern telephone-exchange system ofsubstation-circuits converging to a central station, where by means of asuitable switching apparatus they maybe united in pairs for throughcommunication.

The several substation-circuits are exemplified by two main circuits L Land the switching apparatus is exemplified by a single switch-cordcircuit or system IV.

In the said drawing, A and A represent the substations of the maincircuits L and L respectively, and M is the central station. Thesubstation apparatus is of standard type, as is also the call-receivingportion of the central-station appliances. The substation apparatuscomprises, as usual, the callbell d, the condenser c, thetelephone-transmitter T and receiver t, and the suspensionswitch 8,havingahook termination, on which, as shown at substation A the receiveris hung when not being used. Then the switch 3, in virtueof the presenceof the telephone on the hook, is in its lower position, the circuit isconductively open, the condenser 0 being interposed therein, but thebell (l is of course readily operated through the condenser by thealternating call-currents of the regular generator; but when thereceiver is taken from the hook and the switch 3 moves to its upperposition the circuit is conductively closed through the switch-lever,its contact-stop y, and the station-telephones.

J J are the spring-jacks or switch-sockets of main circuit L, and J Jthe sockets of main circuit L and each contains a contact connection ofboth main wires a b or a b of the circuit. In the sockets J J 3 3 arethe contact-springs extending from condutor b, and 4 4 those which arebranched from conductor a. The socket-frames e of the saidswitch-sockets are grounded through conductor 5 and through anappropriate resistance, which, as shown, may take the form of a cut-offrelay R operating when excited to sever the normal line-terminals 8 and9 at the points 6 and '7when the circuitis transferred to a switch-cordby the insertion of a plug in any one of its sockets. The said conductor5, extending from the switch sockets to ground G or return, forms partof local circuit f, which includes the said cut-oft relay or resistanceand which, as presently to be described, is associated with theanswering switch-plug and the corresponding supervisory signal. Thenormal terminals of the substation-circuits are as usual.

The main conductor aextends through the cut-off relay-contact 6 andextension-conductor to earth, and conductor 1) extends through cut-01frelay-contact 7, the winding of line signal-relay R and the source ofcur rent E to earth. The said line-relay R controls the call-signal D ina normally open local circuit 12 of the generator E which extendsthrough the armature h of the line-relay and its front contact 10 andalso may include an appropriate resistance j. The said signal is shownas being a small glow-lamp, and the said generator E may be andgenerally is a voltaic battery-and the same battery as that to whichreference will presently be more particularly made as being that whichsupplies current for the transmitters and signals for lines which are inuse or active operation.

P is the answering switch-plug, and P the companion switch-plug, of theswitch-cord circuit or system W; I, the usual split winding repeatinginduction-coil; 25 a receiver symbolizing the operators telephoneapparatus; 70, a ringing-key, and F a call-current generator. The tipand ring contact-surfaces p and p of the two plugs, arranged when theplugs are inserted in the sockets J to register and make contact withthe springs 3 and 4, respectively, of said sockets, are united by themain cord-conductors 15 and 16. The battery E, having the usual groundconnection 26, is bridged between the said conductors at the middle ofthe two windings of the split repeating-coil I, and the main cordconductors are thus divided into main-circuit loops X and Z, the formerassociated with the answering-plug, P and the latter with the companionplug P and each constituting the terminal loop or section of the main orsubstation circuit with which its associated plug is or is about to beconnected.

R is the supervisory relay associated with the answering-plug end of thecord-circuit, and R the supervisory relay of the companion plug. Theserelays are in the main-circuit loops Xand Z, respectively, and of coursewhen the plugs are inserted in the sockets of substation-circuits L andL are brought directly into the said circuits and are thereby madesubject or responsive to the operation of the substation-switches s and8 The signal S, preferably also a small glowlamp, is connected in thelocal-circuit conductor 20, which forms part of the local circuit f, thesaid circuit being completed when the plugP is inserted in a socket J ofthe calling-line by way of the frame-piece e of said socket and cut-offrelay R The said local-circuitconductor extends from the ungrounded poleof battery E through said lamp-signal S and a reducing-resistance r tothe sleeve-contact piece p of the plug P. The signal S associated withthe companion plug P in like manner, is in a similar local circuit f,the cord conductor 20 whereof branches from conductor 20 at anyconvenient point 24. This circuit may also have a steadying or reducingresistance 0"" H is a normally open shunt around the signal S, beginningat point 24 of conductor 20, ending at point 17 of the same conductor,and leading by conductor 26 through the restingcontacts n and 27 of adevice hereinafter to be described and byconductor 22 throughthecontact-points 18 and mof the supervisory relay R and throughresistance r. This shunt is therefore controlled by the said relay,being closed when the relay is excited and attracts its armature andopened when the said relay is not excited, and is thus enabled tocontrol the display of the signal S,

With the companion plug is associated a second or auxiliary localcircuit W, the cord portion of which circuit normally extends from anyconvenient point 19 on conductor 22 of the controlling-shunt H byconductor 30 through the contacts of supervisory relay R to any point 53on the ordinary local-circuit conductor 20 on the plug side of theresist ance W.

N is a switching-relay or electromagnetic switch, whose magnet-coilisconnected in the said auxiliary local circuit. The said electromagneticswitch is shown as having two armatures n and o, controlling differentsets of switching-points. Obviously, however, if desired, one armaturecarrying two switching-levers or one armature lever carrying both setsof contacts could readily be arranged. The armature 0' makes noelectrical contact in its quiescent position, but when attracted forwardestablishes contact with its front stop 28. The armature 7% is adaptedto make electrical contacts in both quiescent or back and active or.forward positions and is provided with contiunity-preserving springs qand u, whereby it is enabled to maintain its contact on either sideclosed until that on the other side is established. Its back contactbetween armature n and point27 is in the circuit of thecontrolling-shunt H, and the normal circuit of said shunt, ashereinbefore stated, leads therethrough, so that as long as theelectromagnetic switch remains unactuated the said normal circuit of theshunt H is maintainedthereby. The front contactstop 29 of armature n isbranched from conductor 30 of theauxiliary local circuit within whichthe magnet of the electromagnetic switch is connected, When, therefore,the said switch is operated and the said armature is attracted forward,contact is established between the contact-spring u of said armature andstop 29.

From a point 42 .on the conductor 20 of the regular local circuit f ofplug P a branch connection 32, passing through the contacts 28 and o ofthe electromagnetic switch N, extends to a point 43 on the cordconductor 20 of local circuit f, associated with plug P. Since the saidpoints 28 and o are normally out of contact with one another, thisbranch connection is normally open. VtThen closed at the said contacts,however, by the operation of the switch N, it forms the principalportion of a parallel branch of the said local circuit f of plug P andincludes thesupervisory signal S which is thus connected in parallelwith signal S, the said parallel branch now extending from point 24 byconductor 20 to the said signal S thence to point-42, contacts 2S and o,and conductor 32 to point 43 on conductor 20 of local circuitf. Theportion 30 of the auxiliary local circuit extending between point 19 andthe forward contact-point 29 of armature n of the switch N and passingthrough the contacts 51 52 of the supervisory relay R becomes when saidelectromagnetic switch is operated a continuation of the shunt H,whichis thus extended around both of the two signals S S connected inparallel, and exercises control over both, and since the said shuntnowincludes the contacts of both relays, so that it is controlled byboth relays, it follows that thedeenergization of either relay pursuantto the replacement of the receiver at the substation of either linewilloperate both of the said signals. Thus the display of both signalstogether can only occur when after both receivers have been removed fromtheir respective switclrhooks one or both are replaced.

The operation of the electromagnetic switch has still another result. Ittransfers its own auxiliary local circuit from its original path throughthe contacts 51 and 52 of supervisory relay R to the forward contacts toand 29 of its own armature n, and thus becomes independent of saidrelay-contacts.

The operators telephone t is adapted to be bridged in a well-knownmanner between the main conductors 15 16 of the cord-circuit by means ofthe usual listening-key, which is conventionally indicated by thecontacts 14.

The ringing-key Z6 is adapted when pressed to sever themain conductorsof the main loop Z by separating the springs o w from the contact-points34 and 35 and to connect the former'. to. the terminal contacts 32 and33 of the call-generator F for the purpose of sending a ring orcall-signal over circuit Z to the substation A In these devices theseveral re- ICC sistances should, of course, be proportioned on properengineering principles. Good results will be attained by giving to thecut-off relays a resistance of about thirty ohms, the resistance-coils rand r eighty ohms, and the shunt resistance r twenty ohms. In theoperation of these devices a call coming in over substation-circuit Lwill be responded to by inserting the answering-plug P into socket JSince the receiver at the calling-substation has already been taken fromthe hook to give the call and order, the circuit of battery E is closedthrough the relay R, which therefore is excited. At the same time thelocal circuit fis closed from the battery E to ground by way of thesignal-lamp S, the socket-ring c, and the cut-off relay R but the saidsignal S isnotdisplayed,because thecontrolling-shunt H thereof is closedaround it by the relay R, which being excited has attracted its armatureand brought its contacts on and 18 together, the shunt for the presentbeing maintained through the armature and back contact n and 27 of theswitching-relay N. The signal S though notdisplayed remains under thecontrol of the switch 3 at substation A in the usual way, so that if thesubscriber at any time prior to the culmination of the call wishes toattract the attention of the central operator he may do so byoscillating his switchlever, which will cause the signal to operate thesignal intermittently. The calling subscriber having stated his orderplug P is placed in a switch-socket of the circuit of the wanted.substation, and the local circuit f of said plug being thereby closedcurrent flows through signal S and causes the same to be displayed. Thecall is now sent over line L by operating the ringing-key It. At thisjuncture signal S remains undisplayed, because the receiver 25 atsubstation A has been taken from the hook to send the call and give theorder and has not been replaced, and signal S is displayed because itscircuit 5 f? is closed through the local contacts of the plug P andsocket J and its display continues until the subscriber at A responds tothe call by removing his receiver from the hook 3 but when the receiveris lifted from the switch-hook the main circuit is conductively closedthrough the telephones, and the current from the source E circulatestherein and energizes the supervisory relay R which bringing itscontacts 51 and 52 together closes the auxiliary local circuit 7L2 andcauses the operation of the electromagnetic switch N included therein.The said electromagnetic switch then attracts both armatures by armature0 closing the branch 32 of the local circuit f of plug P through signalS and thus placing the two signals S and S in parallel with one anotherbetween the points 24 and 43 and by armature n uniting the spring andfixed contacts a and 29 and immediately thereafter separating the springcontact (1 from the backstop 27, thereby closing the extendedshunt-circuit around both signals and through the contacts of bothrelays R and R in series and transferring the control of the switch Nfrom the contacts of relay R to its own contacts to and 29. As has beenindicated, the signals S S though now undisplayed remain during thependency of the communication under the control of thesubstation-switches s 5 in such manner that the restoration of thereceiver to the hook at either substation will cause the display of bothsignals S S at the same time, for when either subscriber hangs up histelephone his main circuit is opened at the switch, and thecorresponding relay R or R becomes deenergized, and as the shunt aroundboth lamps leads through the contacts of both relays it will evidentlybe broken by the retraction of the armature of either relay. Receivingthe disconnection-signal the operator pulls the switch-plugs from theirsockets. The circuit maintaining the magnetization of theswitching-relay N, which upon the initial operation of the same wasformed through the forward contacts u and 29, through the winding ofsaid relay, and by conductor 30 to the sleeve contact of plug Preturning thence by way of the switch-socket earth branch, whichcontains the cut-out relay of main circuit L is broken by the withdrawalof the said plug P and the excitement of the magnet of the switch-relayN ceases, permitting it's armatures to move to their original positions,and thus restoring all portions of the switch-cord apparatus to theirnormal or resting state.

Thus by means of my improved supervisory switch-cord circuit a new anddistinctive signal is obtained from the same two lamps viz., the displayof both at the same time-to indicate the requirement of disconnection,even though at the close of the communication but one of thesubstation-receivers be replaced upon its book.

Having now fully specified my invention and its mode of operation, Iclaim 1. In a telephone-system switchboard apparatus, the combination ofanswering and companion switch-plugs, united by a switchcord comprisinga main-circuit loop and. a local signal-circuit conductor for each plug;a supervisory relay included in the main-circuit loop of each plug, asupervisory signal for each plug in the local circuit thereof; ashunt-circuit around the answering-plug signal and including theswitch-points of the answering-plug relay; and means controlled by thecompanion-plug relay and operating pursuant to the excitement thereof toconnect both of the said supervisory signals in parallel branches of theanswering-plug local circuit, and to connect the switch-points of bothsupervisory relays in series in said shunt-circuit, whereby both signalsare rendered responsive to the denergization of either relay;substantially as described.

2. In a telephone-system central-station apparatus, the combination withanswering and of; a supervisory signal associated with each plug in thelocal circuit thereof; and a shuntcircuit around said signal normallycontrolled by the relay of the answering-plug only; of a normally openbranch circuit parallel to the local-circuit conductor containing, saidanswering-plug signal, adapted when closed to include the supervisorysignal of said companion plug; a normally disconnected continuation ofsaid shunt-circuit adapted to extend the same through the contacts ofthe companion-plug relay and to shunt the companion-plug signal alsowhen thus included in said parallel branch; and an electromagnetic orrelay switch controlled by the said supervisory relay ofthe companionplug, and adapted when actuated to close said parallel branch throughsaid companion-plug signal, and to extend said shunt through saidcontinuation; whereby both supervisorysignals may be made responsive toeither supervisory relay, substantially as described.

3. Ina telephone-system switchboard apparatus, the combination ofanswering and companion switch-plugs united by a switchcord comprising amain-circuit loop for each plug, a local signal-circuit conductor foreach plug, and an auxiliary local-circuit conductor for said companionplug; a supervisorysignal associated with the answering-plug andconnected in the local circuit thereof; a normally incomplete branch ofthe said answering-plug local circuit arranged in parallel with thesignal thereof; a second supervisory signal connected in the localsignaling-circuit of the companion plug and also in the said normallyincomplete branch of the answering-plug local circuit; a shunt-circuitnormally around the said first-named signal but adapted when the saidbranch is completed to be extended also around the said second signalincluded therein; a supervisory relay in the main-circuit loop of theanswering-plug and adapted to alone control said shunt as normallyconstituted; a second supervisory relayin the maincircuit loop of thecompanion plug normally controlling the said auxiliary local circuit butadapted when the said shunt is extended around both signals to controlthe same jointly with said first-named relay; and an electromagneticswitch in said auxiliary local circuit maintainingwhen quiescent thenormal circuit of said shunt, but adapted when excited to close saidnormallyincomplete branch through said second signal, and to extend thesaid shunt-circuit around both signals and through the contacts of bothrelays; whereby both signals originally responsive each to its own relayalone, are made responsive to the deenergizat-ion of either relay;substantially as described.

4:- In aswitch-cord-circuit system, the cornbination with the answeringand companion switch-plugs of said cord; the standard main and localcircuits of the said plugs respectively; the supervisory relays andlamp-signals connected in said main and local circuits respectively; andthe standard controllingshunt of the signal-lamp of the answeringpluglocal circuit; of an auxiliary local circuit associated with saidcompanion plug; and an electromagnetic switch included therein,responsive to the supervisory relay of said companion plug; the saidswitch being organized when operated, to connect said signals inparallel branches of the answering-plug local circuit, to establish saidcontrollingshunt around both'signals, and to connect the contacts ofboth supervisory relays in series in said shunt-circuit; whereby thesignal: lamps normally responsive each to its associated relay arebrought into such relation that both are responsiveto either relay;substantially as described.

5. In a telephone-exchange system, the combination of two main orsubstation circuits, viz: acalling and a called circuit, both adapted tobe closed and opened by the substation hook-switch as the receiver istaken therefrom 'or replaced, and both having switch-sockets comprisingmain and local circuit switch contacts at the central stations;'

a switch-cord with answering and companion switch-plugs, and containingmain conductors with a source of current bridged between them anddividing the same into loops, one for each plug, and a localsignal-circuit conductor for each plug; a supervisory relay in eachmain-circuit loop responsive to the operation of the respectivesubstation switchhooks; a supervisory signal for each plug in the localcircuit thereof; a shunt normally arranged around the answering-plugsupervisory signal and controlled by the relay of said answering-plugmain loop, but having an alternative circuit around both supervisorysignals, and through the switch contacts of both supervisory relays; anormally open branch circuit in parallel circuit with the supervisorysignal of the answering-plug and adapted when closed to include theother signal; and an electromagnetic switch or switching-relaycontrolled by the supervisory relay of the companion plug, the saidswitchingrelay having two positions, and being adapted in its quiescentposition to maintain the normal circuit of said shunt, but in its activeposition to close the said parallel branch circuit through saidcompanion-plug signal, and to establish the alternative circuit of saidshunt; substantially as and for the purposes specified.

6. Inatelephone-exchange,acompoundcircuit extending between twosubstations and comprised of two substation-circuits switched togetherat a central-station switchboard on the call of oneof them, and having abattery bridged between its main conductors at said central station;aswitch at each station each controlling the conductive continuity ofits own component circuit; a relay at the central station in each of thesaid component circuits responsive to the switch at the substation ofits own circuit only; alocal circuit associated with each component maincircuit; a supervisory signal included in each local circuit; anauxiliary local circuitassociated with, and leading through the contactsof the relay of the called component main circuit; a shuntcircuit forthe signal of the calling component circuit leading through the contactsof the corresponding relay; a continuation thereof normallydisconnectedbut adapted to extend the same around both signals and through thecontacts of both relays; a normally incomplete branch for the localcircuit associated with the calling component main circuit in parallelwith the signal included in said local clnde the signal of the otherlocal circuit; and an electromagnetic switch connected in the saidauxiliary' local circuit, and adapted in its quiescent position tomaintain the normal circuit of said shunt, but when operated toestablish parallel connection of the said two signals, to transfer itsown local circuit from the contacts of the called-circuit relay tocontacts controlled by its own magnet, and to extend the shunt-circuitthrough the said continuation thereof; substantially as described.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 20th day of June, 1902.

DAVID S. HULFISH. Witnesses 1 L. G. RICHARDSON,

A. B. RAYMOND.

